Plasma processing apparatuses are used to process substrates by processes including plasma etching of semiconducting, dielectric and metallic materials, physical vapor deposition, chemical vapor deposition (CVD), ion implantation and resist removal. Such substrates include, for example, semiconductor wafers and flat screen displays. The substrates can have various regular and irregular shapes and sizes.
A plasma processing apparatus used in semiconductor material processing includes a reaction chamber in which a substrate to be processed is supported on a substrate support. Process gas is introduced into the reaction chamber by a gas distribution system and an energy source energizes the process gas to generate a plasma. During plasma etching processes, the substrate is etched by interaction with the plasma. During deposition processes, material is deposited on the substrate.
During plasma processing of substrates in plasma processing apparatuses, the pressure within the reaction chamber is controlled. Variations in the reaction chamber pressure can affect substrate processing performance, such as the substrate etch rate or material deposition rates onto the substrate. Accordingly, plasma processing apparatuses include pressure sensors that measure the reaction chamber pressure.
Capacitive manometers have been used as a pressure sensor to measure the reaction chamber pressure in plasma processing apparatuses. Capacitive manometers include a flexible diaphragm having a front side at the reaction chamber pressure and a back side at a set low pressure. The diaphragm is deflected by fluid pressure acting on the front side exceeding the set low pressure acting on the back side of the diaphragm. Deflection of the diaphragm changes the capacitance measured by the manometer, which in turn is related to the reaction chamber pressure. Exemplary capacitive manometers are disclosed in U.S. Pat. Nos. 4,785,669; 5,456,945; 5,759,923; 5,811,685; 5,939,639; 5,948,169; 6,443,015 and commonly-assigned U.S. Pat. No. 6,451,159.